ES2203396T3 - OVEN WITH DEPOSIT FOR MANUFACTURING GLASS PROVIDED WITH A PARTICULAR FLOOR PROFILE BETWEEN THE SUN AND THE NECK. - Google Patents

Abstract

A glass manufacturing furnace composed of an elongated molten glass deposit, said deposit in linear sequential order a melting zone (21), a tuning zone (23), a neck portion (12), a conditioning zone (24) and an outlet channel (14) for the extraction of the glass product, and also includes a hearth (11) extending transversely across the oven at or near the rising end of the tuning zone (23) , characterized in that in the downward direction of the hearth (11) the tank has a floor (6) with a modified profile so that the depth of the tank increases progressively from the top of the hearth (11) to the neck portion (12 ) and decreases progressively from the neck portion (12) to the exit channel (14).

Description

Furnace with glass manufacturing tank provided with a particular soil profile between the hearth and the neck.

The invention relates to a manufacturing oven of glass as used in the manufacture of flat glass. He furnace has an elongated tank for casting, refining and conditioning (homogenization) of the glass and the tank, of according to the invention, it has a floor of modified form for Improve the flow pattern of the glass.

Traditional manufacturing deposits of flat glass include a fade zone, a tune zone, a neck portion narrower than its adjacent areas, a conditioning zone and an exit channel through the which glass product is fed to a training unit of sheets or tapes, such as a flotation tank. The biggest part or all of the heat to melt the raw material and keep it in molten state is supplied from above, usually from gas or oil burners. Ensure that heat reaches everything the material to be melted and maintain a temperature of glass high enough in the tank raises a series of problems. Therefore, a great dependence is created in establishing a glass flow pattern inside the reservoir, which achieves a sufficient melting and good homogenization to produce glass of good quality.

Flow pattern control offers a means Useful to regulate the temperature throughout the tank. It is important avoid the presence of both excessively hot regions inside the glass like excessively cold spots: the regions overheated run the risk of damaging the refractory material from which the deposit is made; cold regions can cause solidification or devitrification of glass. Variations excessive temperatures, especially in the downward direction of the melting zone also increases the risk of imperfections in the glass, such as bubbles or bands of parallel striations.

A well-known means to help control the flow is a lateral hearth located at the base of the tank, normally located between the melt zone and the zone of tuned up. FR-A-2737487 describes said solera, the way in which it can be used to divide the tank into ascending and descending sections and illustrates the patterns of Typical flow created in the respective sections.

The soil of each of the zones and portions of the deposit is normal or substantially horizontal, although they have made proposals for soil modeling to improve patterns of glass flow, GB-A-1513653 proposes that a part of the oven floor be inclined towards up towards the floor of the exit channel, overlooking form a neutral zone where the currents are separated towards forward and return. It also proposes that pipes be available cooled with water below the inclined floor portion to promote clear separation of forward currents and of return.

US Patent 2064546 includes a floor tilted up in the "work section" - differentiated from the "melt section" - of a deposit of glass foundry Among several objectives, it aims to regulate the temperature in the working section, facilitating the circulation of return of the coldest glass. In one option, propose a channel deep extending across the width of the section working from the deposit fund and communicating with channels longitudinal slopes adjacent to the side walls of the Deposit. The bottom section of the tank that goes to the canal side bends towards the transverse channel in order to enhance the lateral flow of the glass to the channels Longitudinal

There are problems to ensure control of glass temperature A specific problem arises from the glass that is near the floor of the tank that may be colder, creating the risk of solidification or devitrification. The problems become more apparent with the growing demand for types special colored glass, for example, for the moons of vehicles, which has made it increasingly necessary to undertake production in large-scale plants instead of small ones dedicated ovens that have been used so far. The glass of color, being less thermotransmitter than transparent glass, it poses problems, mainly in the conditioning zone, to ensure uniform cooling and increasing the risk of bands of parallel stretch marks in the melt.

The present invention relates to a tank configuration with glass flow patterns improved

In accordance with the present invention, it is arranged of a glass manufacturing furnace composed of a tank elongated for molten glass, including said deposit in linear sequence a fade zone, a tune zone, a neck portion, a conditioning zone and a canal output for the extraction of the glass product, also included a solera that extends transversely across the width of the oven in or near the ascending section of the tuning zone, characterized in that in the downward direction of the hearth the deposit has a floor with a modified profile so that the Depth of the tank increases progressively from the part top of the hearth to the neck portion and decreases progressively from the neck portion to the canal exit.

The floor of the tank has, therefore, a profile U-shaped shallow in the downward direction of the hearth. It has been found that this form eliminates or substantially reduces the presence in the "dead zones" glass tank overheated or underheated. The absence of a step towards down in the base profile immediately in the downward direction of the solera is especially useful to eliminate the dead zone which is normally created in this area.

The reservoir of the invention offers an advantage considerable to reduce dead zones without resorting to No additional heating inside the tank. The need to heating electrodes, which are expensive and prone to corrosion, is eliminated.

The elevation of the ground in the area of conditioning increases heat losses from the ground, tending to reduce the temperature of the glass and currents traffic. However, since the heat does not penetrate quickly through the colored glass to the portions deep in the conditioning zone in a traditional oven, raising the average soil level increases both temperatures averages such as circulation in the conditioning zone.

It has also been discovered that the U-profile bit deep of the invention considerably reduces any area of solidification in the downward direction of the hearth. In the zone of tuning, the reduced depth of the glass, compared to Traditional ovens, improves gas bubble separation of glass

The modified profile of the tank floor in the descending direction of the hearth must be as uniform as technically possible in line with the fact of being constructed of individual refractory blocks. So, so In general, small steps between blocks are acceptable adjacent, but significant steps have to be avoided.

The floor of the neck portion is preferably horizontal, thus maintaining a depth of uniform glass across the neck and thus facilitating the glass flow through it.

An increase in the temperature of the glass in relation to traditional ovens on the floor of the neck. This may be caused by return currents. coming from the conditioning zone that are hotter than in the traditional oven, possibly because the currents laterals in the conditioning zone descend more quickly That so far.

Another effect of the shallow profile of the invention is that the highest maximum temperatures are achieved by the forward current in the downward direction of The hearth. Globally, glass tuning is better.

The profile from the top of the hearth until the neck opening can be linear, but preferably describes a slight convex curve from a relatively steep slope pronounced initial from the top of the hearth until being substantially horizontal where it meets the floor of neck.

In relation to the soil profile from the neck to the oven exit, that is preferably linear. There seems to be advantages if the base level of the area of conditioning as quickly as possible, but not to the point to give it a concave curvature or introduce steps significant in your profile.

With the modified longitudinal floor profile of the invention, there is no need for complex soil forms at tank width In fact, the lateral shape of the floor of the deposit may be slightly inclined, but preferably it is substantially horizontal, thus giving a uniform depth of wide glass. A slight curvature may be incorporated if you want along the lines where the floor joins the walls lateral, but this does not seem to significantly improve the glass flow pattern.

In the conditioning zone it is important control the rate of heat release through the glass surface. Cooling too fast from the surface tends to cause parallel stretch marks unacceptable thermal in the glass product. The level of risk can be observed by monitoring the number of Rayleigh in the area of the Deposit. The soil profile of the invention offers advantages for reduce the heat shedding of the surface since with the raised floor of the conditioning zone, the glass is cooled more by the floor and the wall of the tank than through the surface. In particular, the temperature level in the channel Exit is much lower, with the consequent reduction in risk of formation of parallel stria bands. This happens in part because the depth of the glass in the tank is reduced increasing the cooling through the ground in relation to the cooling through the surface.

The profile of the deposit according to the invention offers more advantages in relation to the risk of Devitrification of glass. In any glass container by below a temperature of about 1000 ° C there is a risk important devitrification and, especially, in the area of conditioning. The strongest return currents through of the neck of the tanks according to the invention have the beneficial effect of moving up the region with the greatest devitrification potential, thus allowing any Devitrified material dissolves in the tuning zone. The amount of any material devitrified in the sense descending from the hearth is therefore reduced along with the risk that devitrified material can contaminate the channel output

The invention is described below by making reference to the attached figures, where:

Figure 1 is a sectional side view Schematic of a glass manufacturing tank according to the invention;

Figure 2 is a schematic plan view of the glass manufacturing tank of Figure 1.

The illustrated tank, which includes molten glass up to line 10, contains global left glass flows on the right It has a raw material entrance 2, a wall in the rising end 3, walls at the falling ends 4, parallel side walls 5, a floor 6 and a roof (7, 8). There are arranged a lateral hearth 11 on the floor 6 a little ahead of the middle position along the deposit. The shoulders 9 are project into the tank to form a neck 12 a little beyond the middle position of the deposit. An exit channel of the glass 14 is form on the wall of the falling end 4. The walls 3, 4, 5, the floor 6, the ceiling, the hearth 11 and the shoulders of the neck 9 are formed by refractory blocks.

The upper surface portion of the hearth 6 in the upward direction of the hearth 11 is horizontal both in longitudinal as lateral direction. From the top of the hearth 11, the floor 6 has a portion 15 inclined downward in the direction longitudinal to the beginning of neck 12, which again has a horizontal surface In the downward direction of neck 12, the floor 6 has a portion 16 inclined upwards in the direction longitudinal to the outlet channel 14. Portions 15, 16 do not they are tilted in the direction at right angles to the walls lateral 5.

Gas burners (not shown) are located at the rising end of the tank, on the glass line. In the upper part of the neck portion 12 may have been arranged a foam bar 17 forming a small angle with the walls lateral, followed by mixers 18.

Thus the deposit offers in sequential order a fade zone 21, a tune zone 23, a neck 12, a zone conditioning 24 and an output channel 14.

In a typical glass forming operation, Siliceous raw material, including, if required, a proportion of pigment, is melted in zone 21 by the intense heat from gas burners and flows generally in the direction falling. The hearth 11 stimulates a flow of return of matter towards the burners to complete the melting. The tuning of glass, mainly the escape of bubbles, begins when the glass leaves the melting zone 21. The tuning zone 23 tends to extend slightly in the upward direction of the solera 11 as well as descending to neck 12. The Foam bar 17 removes unwanted debris from the surface of the glass as it passes through the neck 12. The 18 mixers provide a degree of agitation to contribute to the homogenization of the glass that reaches the zone of conditioning 24. Glass homogenization continues while passing through conditioning zone 24 and leaving through the channel 14.

The glass that leaves channel 14 turns out to be devitrified material and large parallel stria bands Quality, no bubbles.

Claims (7)

1. A glass manufacturing furnace composed of an elongated molten glass tank, said deposit in linear sequential order a melting zone (21), a tuning zone (23), a neck portion (12), a zone of conditioning (24) and an outlet channel (14) for the extraction of the glass product, and also includes a hearth (11) that extends transversely across the width of the oven at or near the rising end of the tuning zone ( 23), characterized in that in the downward direction of the hearth (11) the tank has a floor (6) with a modified profile so that the depth of the tank progressively increases from the top of the hearth (11) to the neck portion (12) and decreases progressively from the neck portion (12) to the exit channel (14). 2. An oven as claimed in the claim 1, wherein the floor of the tank in the direction descending from the hearth (11) has a uniform profile. 3. An oven as claimed in the claim 1 or claim 2, wherein the floor of the neck portion (12) is horizontal. 4. An oven as claimed in any of the preceding claims, wherein the soil profile of the deposit from the top of the hearth (11) to the Neck opening (12) is linear. 5. An oven as claimed in the claims 1 to 3, wherein the tank floor profile from the top of the hearth (11) to the opening of the neck (12) describes a slight convex curve from a slope initial relatively pronounced from the top of the hearth (11) until it becomes substantially horizontal where it joins the neck floor (12). 6. An oven as claimed in any of the preceding claims, wherein the soil profile of the Deposit from the neck (12) to the exit (14) is linear. 7. An oven as claimed in any of the preceding claims, wherein the lateral level of the tank floor and throughout its length is substantially horizontal.